A retrospective cohort study by researchers at the University of Iowa Carver College of Medicine, posted as a preprint on medRxiv in January 2026, followed about 2.6 million adults who had COVID-19.
The team compared people later diagnosed with Long COVID against matched controls across 15 cardiovascular, renal, and pulmonary outcomes.
The paper has not yet been peer-reviewed.
The list included pulmonary embolism, stroke, kidney disease, and cardiac arrhythmia.
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Long COVID was linked to higher absolute risk on most of those outcomes across adult ages, regardless of sex.
The finding that stood out was not the one many might expect.
Older patients did not carry the largest relative jump in risk. Relative risks were disproportionately higher in younger adults, especially in women for cardiovascular and renal outcomes and in men for selected pulmonary outcomes.
What the study actually measured
The team drew on the TriNetX network, an international federation of electronic health records covering more than 150 million patients.
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From 2,613,432 adults with a documented COVID-19 diagnosis, they identified those later coded with Long COVID, matched them one-to-one with people who had recovered without it, and analysed a matched sample of 315,612 individuals in total.
Age brackets were 18 to 50, 51 to 64, and 65 and older.
The 15 outcomes spanned the heart, kidneys, and lungs.
Because this is observational data pulled from medical records, the study can show association, not causation.
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In a secondary analysis among people with Long COVID, prior SARS-CoV-2 vaccination was not associated with a significantly lower risk of these later complications.
Why the age angle matters
Older adults still carry higher absolute risks.
A 70-year-old is more likely than a 30-year-old to develop heart failure or chronic kidney disease no matter what.
What this analysis shows is that among people who had COVID, the gap in risk between those with Long COVID and their peers without it was widest in the younger age brackets.
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That is clinically relevant because younger adults tend to write off lingering fatigue, breathlessness, or a racing heartbeat as stress, poor sleep, or being out of shape.
Separate NIH RECOVER research has linked Long COVID to new-onset chronic kidney disease and a measurable drop in kidney function within a year of infection.
When to talk to a doctor
The CDC lists a fast-beating or pounding heart and difficulty breathing among the most common Long COVID symptoms.
The agency recommends talking to a healthcare provider about symptoms that are hard to explain or that persist, or if you think you might have Long COVID.
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Severe or worsening chest pain and shortness of breath should be treated as an emergency.
Milder but persistent symptoms that started or got worse after a COVID-19 infection belong at a routine visit, where a provider can decide whether cardiovascular or kidney workup is warranted.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.